FREQUENTLY ASKED QUESTIONS

1.

What is Chandrayaan-1?

Chandrayaan-1 is a scientific investigation – by spacecraft – of the Moon. The name Chandrayaan means “Chandra- Moon , Yaan-vehicle”, –in Indian languages (Sanskrit and Hindi) , – the lunar spacecraft. Chandrayaan-1 is the first Indian planetary science and exploration mission.

2.

When, and from where, Chandrayaan-1 will be launched?

Chandrayaan-1 will be launched in 2008 from Satish Dhawan Space Centre at Sriharikota (SHAR), India.

3.

How long Chandrayaan-1 will take to reach the Moon?

Depending upon the mission strategy, it may vary from 5 days to 20 days.

4.

How close to Moon will Chandrayaan-1 come while orbiting the Moon?

Chandrayaan-1 spacecraft will be in a 100 km polar orbit around the Moon.

What are Chandrayaan's scientific goals?

> To prepare a three-dimensional atlas (with a high spatial and altitude resolution of 5-10 m) of both near and far side of the moon.

> To conduct chemical and mineralogical mapping of the entire lunar surface for distribution of mineral and chemical elements such as Magnesium, Aluminum, Silicon, Calcium, Iron and Titanium as well as high atomic number elements such as Radon, Uranium & Thorium with high spatial resolution.

By simultaneous photo geological and chemical mapping, we will be able to identify different geological units, which will test the hypothesis for the origin and early evolutionary history of the moon and help in determining the nature of the lunar crust.

6.

What are the scientific instruments onboard Chandrayaan-1?

The basic components of the chandrayaan-1 spacecraft are

>The scientific payloads: the instruments that will gather science data.

> The solar array that provides power to the spacecraft. Chandrayaan also carries a battery that stores the power generated by the solar array and feeds it to other systems.

> The thrusters perform fuel burns to change the spacecraft’s trajectory and attitude.

> The spacecraft also carries two star sensors and inertial reference unit based on miniaturised gyros providing absolute attitude.

7.

What are the scientific instruments onboard Chandrayaan-1?

There are altogether eleven scientific instruments onboard Chandrayaan-1 spacecraft. Five of them are Indian and other six are from ESA (3), NASA (2) and Bulgarian Academy of Sciences (1) selected through ISRO Announcement of Opportunity (AO). Two of the ESA instruments have Indian collaboration.

8.

What type of propulsion system will Chandrayaan-1 use? How much propellant will it carry?

Chandrayaan-1 will use bipropellant integrated propulsion system for orbit raising and attitude control. It consists of one 440N engine and eight numbers of 22N thrusters, mounted on the negative roll face of the spacecraft. Two tanks each with a capacity of 390 litres are used for storing fuel and oxidizer.

9.

How will mission controllers communicate with the spacecraft?

If the spacecraft encounters a problem, it can establish contact with controllers on Earth through the Deep Space Network.

10.

Can the team fix the spacecraft from Earth?

If a component on the spacecraft fails, controllers on Earth can instruct Chandrayaan-1 to bring a backup online. If the spacecraft points in the wrong direction, its attitude can be corrected. If the spacecraft deviates from the desired trajectory, a controlled burn (thruster firing) can be performed to put it back on track.

11.

How is the spacecraft powered?

The spacecraft is mainly powered by its solar array, which includes one solar panel covering a total area of 2.15 x 1.8 square meters, generating 750W power. The panels are made of materials rated to withstand extreme temperatures ~110 ºC to -180 ºC. The power produced by the solar array is stored in a Lithium-ion battery, and then distributed from the battery to the spacecraft subsystems. The power system is designed to support various phases of the mission. The power will supplement the mission with equal efficiency in both noon/midnight and dawn/dusk orbits. The power system consists of power generation, energy storage and power conditioning elements. Li-Ion battery powers the spacecraft during eclipse operations. Power electronics system controls the solar array power to supply the load and charge the batteries.

12.

Lunar mission milestones:

The first leap in Lunar observation was made by Galileo Galilei who used his new invention, the telescope to observe mountains and craters on the lunar surface.

The first man-made object to reach the Moon was the unmanned Soviet probe Luna 2 in September 1959. Luna 9 was the first probe to soft land on the Moon in February 1966 and transmit pictures from the lunar surface. The first robotic lunar rover to land on the Moon was the Soviet Lunokhod 1 in November 1970.

Humans first landed on the Moon on July 20, 1969. The first man to walk on the lunar surface was Neil Armstrong, commander of the American mission Apollo 11. The last man to walk on the Moon was in December 1972 by Eugene Cernan during Apollo 17 mission.

Moon samples have been brought back to Earth by three Russian Luna missions (16, 20, and 24) and the US Apollo missions 11, 12 and 14 through 17.

The European Space Agency has launched European spacecraft SMART-1 on September 27, 2003 to explore the Moon, survey the lunar environment and create an X-ray map of the Moon. Japan has launched the lunar orbiter Kaguya (Selene) on September 14, 2007 for observing the distribution of elements and minerals on the lunar surface, study of lunar topography, surface composition, magnetic field and lunar and solar terrestrial environment. China has launched a lunar probe called Chang'e on October 24, 2007 to map lunar surface, measure content and density of lunar soil and explore the environment of the Moon.

India plans to launch a lunar orbiter Chandrayaan-1 for simultaneous photogeological mineralogical and chemical mapping of the lunar surface. The Lunar Reconnaissance Orbiter (LRO) of USA is designed to map the surface of the Moon and Characterise future landing sites in terms of terrain roughness, usable resources, and radiation environment with the ultimate goal of facilitating the return of humans to the Moon.

13.

Comparison between earth and moon

Basic parameters of the earth and the moon

Parameters

Moon

Earth

Ratio

Mass (1024 kg)

0.07349

5.9736

0.0123

Volume (1010 km3)

2.1958

108.321

0.0203

Equatorial radius(km)

1738.1

6378.1

0.2725

Polar radius (km)

1736.0

6356.8

0.2731

Volumetric mean radius (km)

1737.1

6371.0

0.2727

Ellipticity

0.0012

0.00335

0.36

Mean density (kg/m3)

3350

5515

0. 607

Surface gravity (m/s2)

1.62

9.78

0.166

Escape velocity (km/s)

2.38

11.2

0.213

Obliquity

6.7

23.4

0.286

Rotational period

27.32 days

23 hr 56 min 4.09s

1.138

Revolution period

27.32 days

365.26 days

0.0748

Eccentricity

0.055

0.017

3.235

14.

Is there water-ice present on the Moon?

The comets and meteorites continuously bombard the surface of the Moon. Many of these objects contain water and as a result of their impact may leave water molecules on the lunar surface. Solar wind hydrogen bombarding the lunar surface continuously may also lead to production of water molecule through interaction with oxygen present in the lunar soils. Due to solar heating much of this water evaporate and lost into space very fast. However, the current hypothesis is that some of the water molecules may reach areas that are permanently shadowed from sunlight and gets trapped and significant traces of water/water ice may be present in such regions of the Moon.

Due to the very slight "tilt" (~ 1.5°) of the Moon's axis, some of the deep craters particularly near the polar regions never receive any light from the Sun - they are permanently shadowed and can act as permanent trap of water molecules and in such craters scientists expect to find water in frozen form, if it is there at all.

The Radar reflectivity experiments performed by Clementine hinted at the possibility of existence of large amounts of water frozen on these permanently shadowed regions of the moon.

Lunar Prospector's neutron spectrometer detected bursts of slow neutrons over the moon's poles, suggesting presence of hydrogen atoms and hence possible presence of water/ice. However, these experiments could not decisively confirm the presence of water/ice on moon, which still remains a mystery.

If there is water ice present on the Moon then we would not have to transport water from Earth to the Moon, which would be extremely expensive. But instead will be able to rely on lunar ice. This is important for a cost-effective lunar habitation.

15.

What is the temperature on the moon?

The moon undergoes extremes in temperature - the side of the Moon receiving sunlight becomes scorching hot at about 130 ºC, and freezing cold at -180 ºC on the nightside.

16.

Is there any Life on moon?

So far none of the lunar missions have detected any signature of presence of life on the Moon.

17.

Why do we see only one side of the Moon?

As the Moon orbits, it always presents the same side towards the Earth. This is so because Earth's gravity has slowed the Moon's rotation so that it just matches the time it takes to go around the Earth. So the Moon takes the same amount of time to revolve around the Earth as it takes to rotate around its spin axis.

18.

How was the Moon formed?

There are various theories on the evolution of Earth and Moon system. Currently four main hypotheses have been considered to explain the origin of the Moon:

1. Simultaneous Formation:Earth and the Moon were formed from the solar nebula near each other. This theory is able to explain why the Earth and the Moon rocks are isotopically so similar, but cannot explain why the Moon is depleted in Iron (Fe).

2. Capture: Moon formed somewhere else in the Solar System where the iron content was lower. After it formed, it drifted close to the Earth and was captured by the Earth’s gravitational field. This theory cannot explain why the Earth and the Moon rocks are isotopically similar but explains the high angular momentum of the Earth-Moon system.

3. Fission: According to this hypothesis, the Moon broke off from the hot molten Earth while the Earth was spinning very rapidly. This hypothesis can explain why the Earth and the Moon rocks are similar, chemically and isotopically, and the low iron content of the Moon, but is not able to explain the high angular momentum of the Earth-Moon system.

4. Giant-Impact: This hypothesis suggests that a body about 1-3 times the size of Mars impacted on the Earth during the last stages of the Earth’s formation, after the Earth’s iron core has already formed. When the impact occurred, it ejected a large part of the Earth into space and the ejecta then began orbiting the Earth. The material blasted off the Earth coalesced into the Moon. This hypothesis is able to explain (a) the missing Moon iron as most of the material blasted into space would have been depleted in iron, (b) Moon rocks and Earth rocks are isotopically similar and (c) why the Moon’s orbit as well as the Earth’s orbit are tilted. The giant impact hypothesis however have some difficulties since numerical models predict that a large fraction of the Moon would come from the impactor, leading to the same dilemma as the Capture theory.

High resolution Chemical, mineralogical and photo-geological mapping of lunar surface in visible, near IR, low and high energy X-rays

68.

2009

Lunar Reconnaissance
Orbiter

USA

Conduct investigations specifically targeted to prepare for and support future human exploration of the Moon

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